1. Field of the Invention
The present invention relates to a voltage controlled oscillator used in a phase locked loop (PLL) circuit or the like.
2. Description of the Related Art
In a prior art voltage controlled oscillator including an odd number of inverter circuits connected in a ring shape (see JP-A-6-291617), at least one of the inverter circuits is constructed by an inverter and a current control circuit connected in series between a pre-stage inverter circuit and post-stage inverter circuit. The inverter receives an output signal of the pre-stage inverter circuit to generate an inverted signal. The current control circuit supplies a current in accordance with the inverted signal to the post-stage inverter circuit. This will be explained later in detail.
In the above-described prior art voltage controlled oscillator, however, since the input capacitance of the current control circuit is relatively large, the delay time for charging and discharging the above-mentioned input capacitance is relatively large, so that it is impossible to generate a high frequency output signal.